1. Field of the Invention
The present invention relates to a structure of a semiconductor device which can be used for a flat panel display typified by an active matrix type liquid crystal display and an EL type display unit and more particularly to a structure of an inter-layer insulating film of a semiconductor device typified by a thin film transistor.
2. Description of Related Art
Hitherto, an active matrix type liquid crystal display has been known as a typical flat panel display. It has a structure in which a switching thin film transistor is provided in each of a large number of pixels disposed in a matrix and charge input/output to/from each pixel electrode is controlled by this thin film transistor.
In such a structure, it is necessary to coat the semiconductor device by an insulating film to prevent moisture, impurities and moving ions (e.g., sodium ions) which are great enemy of the semiconductor device from infiltrating. Further, it must be constructed such that capacity produced between the pixel electrode, wires and the thin film transistor can be reduced.
Further, it is required to have a low production cost and an excellent productivity. However, it is the present situation that those requirements cannot be met with a silicon oxide film or a silicon nitride film which are normally utilized as an inter-layer insulating film.